Semiconductor device having a liner layer with a configured profile

ABSTRACT

Devices and methods that include for configuring a profile of a liner layer before filling an opening disposed over a semiconductor substrate. The liner layer has a first thickness at the bottom of the opening and a second thickness a top of the opening, the second thickness being smaller that the first thickness. In an embodiment, the filled opening provides a contact structure.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 15/906,092, filed Feb. 27, 2018, entitled “SEMICONDUCTOR DEVICEHAVING A LINER LAYER WITH A CONFIGURED PROFILE AND METHOD OF FABRICATINGTHEREOF”, which claims the benefit of U.S. Provisional Application No.62/527,423, filed Jun. 30, 2017, hereby incorporated by reference intheir entirety.

BACKGROUND

The integrated circuit (IC) industry has experienced exponential growth.Technological advances in IC materials and design have producedgenerations of ICs, where each generation has smaller and more complexcircuits than the previous generation. In the course of IC evolution,functional density (i.e., the number of interconnected devices per chiparea) has generally increased while geometry size (i.e., the smallestcomponent (or line) that can be created using a fabrication process) hasdecreased. This scaling down process generally provides benefits byincreasing production efficiency and lowering associated costs.

Such scaling down has also increased the complexity of processing andmanufacturing ICs and, for these advances to be realized, similardevelopments in IC processing and manufacturing are needed. For example,as semiconductor device features become closer in proximity to oneanother, so do the respective contact elements providing a connection tothe device features. Forming these tightly constrained and often ofsignificant height features can raise processing challenges. Theseprocess margins can be further tightened during FinFET fabricationprocesses. In particular, decreasing fin pitches and increasing finheights are significantly constraining abilities of existing processesfor forming contact features to source and drain or gate features of theFinFET device. Accordingly, although techniques have been generallyadequate for their intended purposes, they have not been entirelysatisfactory in all respects.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 is a flow chart of a method for fabricating a semiconductordevice according to various aspects of the present disclosure.

FIGS. 2-9 are cross-sectional views of a semiconductor devicefabricating according to steps of an exemplary embodiment of the methodof FIG. 1 according to various aspects of the present disclosure.

FIGS. 10-12 are cross-sectional views of a semiconductor devicefabricating according to steps of another exemplary embodiment of themethod of FIG. 1 according to various aspects of the present disclosure.

FIG. 13 is a perspective view of an embodiment of a semiconductor deviceaccording to aspects of the present disclosure.

FIGS. 14A, 14B, and 14C are portions various cross-sectional views of anexample embodiment of the device of FIG. 13, according to some aspectsof the present disclosure.

FIGS. 15A, 15B, and 15C are portions of various cross-sectional views ofanother example embodiment of the device of FIG. 13, according to someaspects of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact.

In addition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.Moreover, the formation of a feature on, connected to, and/or coupled toanother feature in the present disclosure that follows may includeembodiments in which the features are formed in direct contact, and mayalso include embodiments in which additional features may be formedinterposing the features, such that the features may not be in directcontact. In addition, spatially relative terms, for example, “lower,”“upper,” “horizontal,” “vertical,” “above,” “over,” “below,” “beneath,”“up,” “down,” “top,” “bottom,” etc. as well as derivatives thereof(e.g., “horizontally,” “downwardly,” “upwardly,” etc.) are used for easeof the present disclosure of one features relationship to anotherfeature. The spatially relative terms are intended to cover differentorientations of the device including the features.

It is also noted that the present disclosure presents certain exemplaryembodiments in the form of multi-gate transistors or fin-type multi-gatetransistors referred to herein as FinFET devices. Such a device mayinclude a P-type metal-oxide-semiconductor FinFET device or an N-typemetal-oxide-semiconductor FinFET device. The FinFET device may be adual-gate device, tri-gate device, bulk device, silicon-on-insulator(SOI) device, and/or other configuration. One of ordinary skill mayrecognize other examples of semiconductor devices that may benefit fromaspects of the present disclosure. For example, some embodiments asdescribed herein may also be applied to gate-all-around (GAA) devices,Omega-gate (Ω-gate) devices, or Pi-gate (Π-gate) devices. The presentdisclosure also applies equally to planar devices such as planar FETs.

As discussed above, as technology nodes shrink, it becomes morechallenging to fabricate certain aspects of semiconductor devices,including, for example, as widths (e.g., diameters) of openings shrinkit can become more challenging to subsequently fill said opening withmaterial. Typical filling methods can cause quality and/or reliabilityissues such as the formation of seams or voids in the fill material ofthe opening. As but one example, filling the opening formed for contactstructures can cause device performance issues such as higher resistanceof the contact structure due to these seams or voids. Another aspectworth consideration is that it may be desired to fill openings withmulti-layers of materials. For example, liner layers that act as barrierlayers or glue layers can be deposited in the opening to preventdiffusion from the subsequently deposited fill material in the openingto the material surrounding the opening. For example, barrier/gluelayers may be used in contact openings to prevent metal fill fromdiffuses into adjacent dielectric material in the gate structure orinter-layer dielectric (ILD). However, as the width of the openingdecreases with shrinking technology nodes, the required thickness of theliner layer can take up a greater and greater percentage of the opening.In some cases, the liner layer (e.g., barrier/glue layer) can take up ⅓to ¼ of the width of the opening leaving the remaining portion of theopening having a reduced width that is difficult to fill with thelow-resistance contact metal. Challenges in filling the opening can alsobe recognized in deposition methods that cause agglomeration of materialat a top of the opening referred to as “overhang” (e.g., physical vapordeposition).

Certain structures and methods described herein can allow for filling ofan opening formed in semiconductor device fabrication that reduces oreven eliminates the seam and/or void formation and/or reduces otherchallenges discussed above. As discussed in detail below, the methodsand structures in some embodiments provide for a modified profile ofliner layer (e.g., barrier and/or glue layer). The modified profileliner layer exhibits a difference in thickness between various regionsof the layer. The modified profile in some embodiments allows for theliner to function as an appropriate adhesion promoter and/or diffusionprevention layer, while also provided adequate spacing for additionallayers, such as additional metal layers, to be subsequently formedwithin the opening.

FIG. 1 is a flow chart of a method 100 for fabricating an integratedcircuit device according to various aspects of the present disclosure.In the present embodiment, method 100 fabricates an integrated circuitdevice that includes a transistor device such as a FinFET device orplanar FET device having a gate and associated source/drain. FIGS. 2-9are exemplary cross-sections of a device 200 fabricated according tosteps of the method 100. FIGS. 2-9 have been simplified for the sake ofclarity to better understand the inventive concepts of the presentdisclosure. Additional features can be added in the device 200, and someof the features described below can be replaced, modified, or eliminatedin other embodiments of the device 200. It is also recognized that thedevice 200 implies a coplanarity to the contact structures, which isprovided for ease of illustration and not intended to be limiting tothis configuration.

The device 200 includes a semiconductor device of a transistor, whichcan be included in a microprocessor, memory cell, and/or otherintegrated circuit device. Furthermore, the device 200 may be anintermediate device fabricated during processing of an integratedcircuit (IC) chip, a system on chip (SoC), or portion thereof, thatincludes various passive and active microelectronic devices such asresistors, capacitors, inductors, diodes, p-type field effecttransistors (PFETs), n-type field effect transistors (NFETs),metal-oxide semiconductor field effect transistors (MOSFETs),complementary metal-oxide semiconductor (CMOSs) transistors, bipolartransistors, high voltage transistors, high frequency transistors, othersuitable components, or combinations thereof.

The method 100 begins at block 102 where a substrate is provided. Usingthe example of FIG. 2, the substrate 202 is a substrate of the exemplarydevice 200. In an embodiment, the substrate 202 is a silicon substrate(e.g., wafer). Alternatively, the substrate 202 may comprise anotherelementary semiconductor, such as germanium; a compound semiconductorincluding silicon carbide, gallium arsenic, gallium phosphide, indiumphosphide, indium arsenide, and/or indium antimonide; an alloysemiconductor including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP,and/or GaInAsP; or combinations thereof. In yet another alternative, thesubstrate 202 is a semiconductor-on-insulator (SOI) such as having aburied dielectric layer. In embodiments, the substrate 202 includesactive regions such as p-wells and n-wells for forming active devicesand may include interposing isolation regions (e.g., shallow trenchisolation (STI) features).

The substrate provided in block 102 has a contact region where aconductive contact structure is to be formed. The contact structures, asdiscussed below, are formed by creating contact holes in an insulatinglayer to formed electrical connection to the contact areas in thesemiconductor substrate. These contact holes or openings can besubsequently filled with conductive material (e.g., metal) step coverageto insure reliable electrical contact with low contact resistanceprovided there is sufficient step coverage. The contact structure may bebetween a gate structure and an overlying interconnect layer, asource/drain feature, and/or connection between other semiconductordevice components, active or passive and an overlying conductive layer.While a contact structure is formed in the present example, it is notedthat other embodiments that may implement portions of the disclosure mayalso be possible including for example, using the method 100 to providea conductive structure to connect interconnect layers (e.g., alsoreferred to as a via), portions of post-passivation interconnectstructures (PPI), through substrate vias, a replacement gate methodwhere a trench is filled with a metal gate, and/or other features formedon a substrate where a hole or trench is desired to be filled.

In an embodiment, at block 102 a substrate suitable to fabricate aplanar field effect transistor is provided where the substrate includesa channel region under a gate and between a source and drain region. Thecontact structure is desired to be connected to one or more features ofthe planar FET (e.g., gate, source/drain). In an embodiment, at block102 a substrate having a fin structure is provided, where the finstructure includes a channel region under a gate and between a sourceregion and a drain region. The contact structure is desired to beconnected to one or more features of the FINFET (e.g., gate,source/drain). It is noted that the illustrations of the figures of thepresent application apply to each of a planar or a FINFET device (e.g.,the cross-sectional cut being a long a fin represented by 202).Referring again to the example of FIG. 2, the device 200 includes aplurality of gate structures 204 and a plurality of associatedsource/drain regions 206.

The gate structure or gate stack 204 includes a gate dielectric layerand a gate electrode layer. The gate dielectric layer may includesilicon oxide or a high-k dielectric material such as hafnium oxide,zirconium oxide, lanthanum oxide, titanium oxide, yttrium oxide,strontium titanate, and/or other suitable material. The gate dielectriclayer may be formed by chemical oxidation, thermal oxidation, atomiclayer deposition (ALD), chemical vapor deposition (CVD), and/or othersuitable methods. In an embodiment, the gate electrode layer includespolysilicon, and may be formed by suitable deposition processes such aslow-pressure chemical vapor deposition (LPCVD) and plasma-enhanced CVD(PECVD). In some embodiments, the gate electrode layer includes ann-type or a p-type work function layer and a metal fill layer. Forexample, an n-type work function layer may comprise a metal withsufficiently low effective work function such as titanium, aluminum,tantalum carbide, tantalum carbide nitride, tantalum silicon nitride, orcombinations thereof. For example, a p-type work function layer maycomprise a metal with a sufficiently large effective work function, suchas titanium nitride, tantalum nitride, ruthenium, molybdenum, tungsten,platinum, or combinations thereof. For example, a metal fill layer mayinclude aluminum, tungsten, cobalt, copper, and/or other suitablematerials. The gate electrode layer may be formed by CVD, PVD, plating,and/or other suitable processes.

In FIG. 2, in some embodiments, the gate structure 204 is a polysilicongate. In some embodiments, the gate stack 204 is formed by a replacementgate process such as that including forming a sacrificial gatestructure, i.e., a placeholder for a final gate stack. In someembodiments, the gate structure 204 includes an interfacial layerbetween its gate dielectric layer and a channel region of the substrate202. The interfacial layer may include a dielectric material such assilicon oxide or silicon oxynitride, and may be formed by chemicaloxidation, thermal oxidation, ALD, CVD, and/or other suitabledielectric. The gate structure 204 may include other layers such as hardmask layer(s) (see hard mask layer 204A below).

Spacer elements 210 abut the sidewalls of the gate structure 204. Thespacer elements 210 may include one or more layers of dielectricmaterial providing for example, seal spacers and/or offset spacers.Exemplary dielectric compositions for the spacer elements 210 includesilicon oxide, silicon nitride, silicon oxynitride, silicon carbide,other suitable material, or combinations thereof. In some embodiments,the spacer elements 210 are formed by depositing dielectric materialover the substrate 202 and the gate structure 204 and subsequentlyanisotropically etching the material to form the spacer elements 210.During the etching processes, dielectric material of the spacers isremoved from a portion of substrate 202, more particularly, over thesource/drain regions 206. Implantation, diffusion, and/or annealingprocesses may be performed to form lightly doped source and drain (LDD)features in source/drain regions 206 before and/or after forming spacerelements 210.

The source/drain regions 206 are disposed adjacent the gate structures204. In some embodiments, the source/drain regions 206 are suitablydoped regions of the substrate 202. In some embodiments, thesource/drain regions 206 are epitaxially grown material (e.g., that maybe the same or different in semiconductor composition than the substrate202). The source/drain features 206 are doped with n-type dopants and/orp-type dopants to provide suitable conductivity to form the device 200.The dopants may be introduced by ion implantation, diffusion, during theepitaxial growth process, and/or other suitable processes. In someembodiments, the introduction of the dopants is followed by an annealprocess.

For example, in some implementations, where the device 200 is configuredas an n-type device (for example, having an n-channel), source/drainfeatures 206 include silicon or silicon carbon that is doped withphosphorous, arsenic, other n-type dopant, or combinations thereof (forexample, forming Si:P epitaxial layers or Si:C:P epitaxial layers). Insome implementations, where the device 200 is configured as a p-typedevice (for example, having a p-channel), the source/drain features 206include silicon germanium (SiGe) doped with boron, other p-type dopant,or combinations thereof (for example, forming a Si:Ge:B epitaxiallayer).

A silicide region 208 is disposed on a top region of the source/drainregions 206. The silicide region 208 includes a metal silicidecomposition. The metal silicide may include nickel silicide, cobaltsilicide, tungsten silicide, tantalum silicide, titanium silicide,platinum silicide, erbium silicide, palladium silicide, or combinationsthereof. The silicide region 208 may be a portion of the source/drainfeatures 206 (e.g., lie below a plane coplanar with a top surface of thesubstrate 202). The silicide region 208 may be formed by depositing ametal composition over the source/drain features 206 and performing ananneal to form the silicidation of a top portion of the source/drainfeatures.

A dielectric layer 212 is disposed over the substrate 202; thedielectric layer 212 is also referred to as an interlayer dielectric(ILD) layer. The dielectric layer 212 may be formed by a depositionprocess (such as chemical vapor deposition (CVD), physical vapordeposition (PVD) or other suitable methods). Dielectric layer 212includes a dielectric material, such as silicon oxide, silicon nitride,silicon oxynitride, TEOS formed oxide, phosphosilicate glass (PSG),borophosphosilicate glass (BPSG), low-k dielectric material, othersuitable dielectric material, or combinations thereof. Exemplary low-kdielectric materials include fluorinated silica glass (FSG), carbondoped silicon oxide, Black Diamond® (Applied Materials of Santa Clara,Calif.), Xerogel, Aerogel, amorphous fluorinated carbon, Parylene, BCB(bis-benzocyclobutenes), SiLK (Dow Chemical, Midland, Mich.), polyimide,other proper materials, or combinations thereof. In some embodiments,dielectric layer 212 is a low-k dielectric layer. In someimplementations, dielectric layer 212 can include a multilayer structurehaving multiple dielectric materials.

It is noted that a contact etch stop layer (not specifically enumerated)may be disposed between the gate structure 204 (spacer elements 210) andthe interlayer dielectric (ILD) 212.

Having provided a substrate having a plurality of features and/or layersdisposed thereon with a contact region defined, the method 100 thenproceeds to block 104 where openings (also referred to as holes ortrenches) are formed in a layer(s) in the contact region in order toexpose a top surface of an underlying feature. In an embodiment, one ormore openings expose a surface of the source/drain region 206(specifically the silicide 208 of the source/drain region 206). In anembodiment, one or more of the openings expose a top surface of the gatestructure 204. The top surface of the gate structure may be conductivesuch as, silicide or the conductive fill metal of a metal gate structuresuch as tungsten. The openings may be formed by a suitable lithographypatterning followed by etching processes such as a dry or plasma etchingprocess. The openings for different feature types (e.g., gate andsource/drain) may be formed simultaneously or in different steps. Insome embodiments, the openings may have a width of between approximately15 nanometers (nm) and 50 nm. It is noted that the cross-sectional viewof FIG. 2 illustrates contact holes for both the source/drain features206 and the gate structure 204. This is for ease of illustration anddoes not imply that a contact structure to a gate is coplanar with thatof the source/drain feature. In other embodiments, at a region coplanar(e.g., perpendicular plane to a top surface of the substrate 202) withthe source/drain contact opening 214, the gate structure 204 may havedielectric disposed there over (e.g., a hard mask layer and then thedielectric layer 212). In an embodiment, the contact opening 214 has anaspect ratio (who) of at least 1:5.

Referring to the example of FIG. 2, contact holes 214 are formed in thedielectric layer 212. The contact holes 214 as illustrated expose a topsurface of the gate structure 204 and a top surface of the source/drainfeature 206 (e.g., silicide 208). It is noted that in at least someembodiments, the silicide feature 208 is formed after etching thecontact holes 214. For example, the openings 214 expose the source/drainfeatures 206 and a silicidation (which may include agermano-silicidation) forms the silicide 208. For example, silicidationmay be formed by depositing a metal layer (e.g., a portion of the linerlayer discussed below or a separate layer) over the exposed portion ofthe source/drain feature 206 (e.g., epitaxial layer), annealing themetal layer such that the metal layer reacts with silicon in thesource/drain features 206 to form the metal silicidation, and thereafterremoving the non-reacted metal layer (if any). In other embodiments, asdiscussed below, the deposition of the liner layer in block 106 providesthe metal composition to form the silicide feature 208. After formingthe contact openings 214, a cleaning process may be performed (e.g.,sputtering of inert gas). The cleaning process may remove undesirednative oxide at the bottom of the opening.

The method 100 then proceeds to block 106 where a deposition of a linerlayer is formed in the contact holes. The liner layer may also bereferred to as a glue (or adhesion) layer (e.g., to improve adhesionbetween an overlying layer and the sidewall of the opening) and/orbarrier layer (e.g., to prevent diffusion). In an embodiment, the linerlayer is configured (e.g., thickness and composition) to prevent metaldiffusion into adjacent features (e.g., gate structure 204 and/ordielectric layer 212). In an embodiment, the liner layer is configured(e.g., thickness and composition) to improve adhesion between asubsequently deposited conductive fill of the opening with dielectricsidewall materials (e.g., dielectric layer 212 such as SiN/SiO2).

In an embodiment, block 106 deposits a liner layer of a metal such astitanium (Ti). In some embodiments, the metal (e.g., titanium) isdeposited by physical vapor deposition (PVD) or other suitabledeposition methods. The liner layer of metal may be deposed on thesidewalls and bottom of the openings 214. The Ti may interface thesource/drain feature 206. A silicidation (which may include agermano-silicidation) is then performed to form the silicide 208 usingthe titanium and annealing the substrate such that the metal (e.g., Ti)liner layer reacts with the semiconductor (e.g., silicon) in thesource/drain features 206 to form the metal silicidation.

In an embodiment, the liner layer includes in lieu of the metal layer orin addition to the metal layer (e.g., Ti), a metal nitride compositionsuch as TaN, TiN, TiSiN, TaSiN, may be used. In an embodiment, the metalnitride composition is disposed directly on and over the first metal ofthe liner layer. In some embodiments, the metal of the liner layer isomitted and the metal nitride layer is disposed in the opening on thesidewalls and/or bottom of the openings. Thus, in some embodiments,where the liner layer includes a dielectric material interfacing thesidewalls of the opening, the silicide feature 208 may be formed priorto the deposition of the dielectric barrier layer. The metal nitridematerial such as TaN or TiN may be formed by chemical vapor deposition(CVD) and/or other suitable deposition methods.

Referring to the example of FIG. 3, illustrated is a liner layer 302. Asdiscussed above, in an embodiment, the liner layer 302 includes a metalsuch as titanium. In an embodiment, the liner layer 302 of titanium isdeposited and then annealed to form the silicide region 208. In anotheror further embodiment, the liner layer 302 includes TiN. For example,TiN may be formed on a metal layer such as Ti. Other examples of theliner layer 302 include TaN. In some embodiments, the liner layer 302 isa combination of layers discussed above including for example a layerhaving a stack of Ti/TiN.

In an embodiment, the liner layer 302 has a thickness of t1, t2 and t3as deposited. In an embodiment, t1, t2 and t3 are substantially equal inthickness (where substantially includes thickness variations typicalwith a process such as, 10% or less). In an embodiment, t1, t2, and/ort3 may be between approximately of approximately 10 and 30 Angstroms. Insome embodiments, the thicknesses t1, t2, t3 are provided for acomposition of materials or layers (e.g., Ti and TiN) forming the linerlayer. In other embodiments, the thicknesses t1, t2, and t3 are a singlecomposition.

In some embodiments, the liner layer 302 is a metal that is used to formthe silicide 208. Thus, after deposition of the liner layer 302 atthickness t1 at the bottom of the opening 214, the metal portion (e.g.,Ti) of the liner layer 302 may be consumed in whole or in part at thebottom of the opening 214 during the silicidation of the source/drain206. While not specifically illustrated, in some embodiments, the linerlayer 302 is also disposed on a top surface of the dielectric layer 212.The liner layer 302 on the dielectric layer 212 may be subsequentlyremoved by a planarization process.

The method 100 of FIG. 1 then proceeds to block 108 where a maskinglayer is formed in the opening of the contact. The masking layer may beformed over a portion of the liner layer deposited in block 106. Themasking layer may include a bottom antireflective coating (BARC)material. “BARC” materials can refer to organic and inorganic BARCmaterials. Organic BARCs include, but are not limited to, polysulfones,polyureas, polyurea sulfones, polyacrylates and poly(vinyl pyridine).Inorganic BARCs include, but are not limited to, silicon oxynitrides(SiOxNy). Other examples of the masking material include photoresist,polymers, and/or other suitable material.

In some embodiments, the masking material is deposited by a suitabledeposition process such as, spin on coating, CVD, or other suitabledeposition process and subsequently the material is etched back to adesired height. The etchback may maintain the masking material in thecontact opening at a height that is a greater distance from a topsurface of the substrate than a top surface of a gate structure.

Referring to the example of FIG. 4, a masking material 402 is formed inthe contact opening 214 over the liner layer 302. The masking material402 has a height h1 from a top surface of the semiconductor substrate202. The gate structure 204 has a height h2 from a top surface of thesemiconductor substrate 202. h1 is greater than h2. In an embodiment, h1is between approximately 20% and 50% greater than h2. Having h1 greaterthan h2 can mitigate or prevent damage to gate materials (e.g., workfunction metals) of the gate structure 204 below the contact opening214.

The method 100 then proceeds to block 110 where a portion of the linerlayer is removed from the opening while using the masking layer as amasking element. Thus, the etching process of block 110 may be selectiveto the liner layer material. In an embodiment, the removal of theportion of the liner layer is performed by a wet etching process. In anembodiment, the etching process is acid-based. In some embodiments, theetching includes Hcl:H2O2:H2O(“standard clean 2” or SC2). In otherembodiments, other etchants are used that maintain a selectivity to theliner layer, while reducing or eliminating the etching of the maskinglayer.

Referring to the example of FIG. 5, while the masking layer 402 isdisposed in the opening 214, the exposed liner layer 302 is removed froma top portion of the sidewalls of the opening 214. The liner layer atportions under the masking element 402 is maintained, denoted now asremaining or etched liner layer 502. In an embodiment, the etchingcontinues to substantially or wholly remove the liner layer 302 from theupper portions of the sidewalls exposing the dielectric 212 asillustrated. In other embodiments, a thin film of the remaining linerlayer 502 (e.g., residual) may be maintained on the upper sidewalls ofthe opening 214.

The method 100 then proceeds to block 112 where the masking layer isremoved from the opening. The masking layer may be stripped from thesubstrate. In an embodiment, the masking layer is removed by an ashingprocess. Referring to the example of FIG. 6, the masking layer 402 hasbeen removed from the openings 214.

In an embodiment of the method 100 of FIG. 1, the method 100 after block112 proceeds to block 116 where another (e.g., second) deposition of oneor more of the materials of the liner layer is performed. The linerlayer deposited in block 116 may be the same composition as thatdeposited in block 106, described above. In an embodiment, the linerlayer deposited in block 116 is TiN or TaN. In an embodiment, the linerlayer deposited in block 106 includes Ti followed by TiN and the linerlayer in block 116 includes only TiN.

The second deposition of material of the liner layer in block 116 mayinclude depositing material on the upper sidewalls of the contactopening (e.g., where the liner layer has been previously removed), thelower sidewalls of the contact opening (e.g., where the previouslydeposited liner layer may remain), and the bottom of the opening (e.g.,where the previously deposited liner layer may remain). The depositionof block 116 may be performed by CVD or other suitable depositionmethods.

Thus, the resultant liner layer provided by the embodiment of the method100 has a different thickness at the bottom of the opening and the lowersidewalls of the opening than the upper sidewalls. This is because theportions of the liner layer at the lower sidewalls and bottom includematerial from the first deposition (block 106) as well as the seconddeposition (block 116), while the upper portion of the liner layeradjacent the upper sidewalls of the opening is thinner as it includesmaterial only from the second deposition (block 116) or a thinnerresidual material from the first deposition (block 106) and materialfrom the second deposition (block 116). Following the composition of theupper portion may be dictated by the deposition of the block 116, whilethe composition of the portion of the liner layer at the lower sidewallsincludes that of both deposition steps.

Referring to the example of FIG. 7, the liner layer 702 has been formedby performing a second deposition of liner layer material on theremaining liner layer 502 of FIG. 6. The liner layer 702 has a thicknesst4 at the upper sidewalls of the opening 214 (e.g., sidewalls greaterthan height h1). The liner layer 702 has a thickness t5 at the lowersidewalls of the opening 214 (e.g., less than height h1). The linerlayer 702 has a thickness t6 at the bottom of the opening 214. t5 and t6may be substantially equal. t5 and t6 may each be greater than t4. In anembodiment, a ratio of t5 (or t6) to t4 is approximately 2:1. In anembodiment, a ratio of t3:t4 may be approximately 1:2. It is reiteratedthat t5 and t6 result from the liner layer deposited in block 106 andblock 116.

It is noted that because the liner layer is thinner at a top portion ofthe opening (e.g., t4), depositing additional layers over the linerlayer can be performed in some embodiments such that there is amitigation or prevention of formation of metal seam/void defects in thecontact structure. This is because the available width of the remainingopening is greater. It is also noted that the thickness t6 should becontrolled to account for the trade-off between barrier integrity withcontact resistance, e.g., the thicker t6 the greater the barrierintegrity at the expense of increasing contact resistance. It isrecognized however in some embodiments that t4 must be maintained suchthat it is sufficient to continue to prevent diffusion (e.g., between802 and 212).

The method 100 continues to perform a metal fill of the opening havingthe liner layer to form the contact structure. In an embodiment, ametal-containing fill layer of conductive material or materials isdeposited into the contact hole. For example, an aluminum-containingmetal fill layer may be deposited. Other exemplary materials includealuminum, aluminum alloy (such as aluminum/silicon/copper alloy),copper, copper alloy, titanium, titanium nitride, tantalum, tantalumnitride, tungsten, polysilicon, metal silicide, other suitable metals,or combinations thereof. The metal silicide may include nickel silicide,cobalt silicide, tungsten silicide, tantalum silicide, titaniumsilicide, platinum silicide, erbium silicide, palladium silicide, orcombinations thereof. In some embodiments, the metal fill layer 802includes a plurality of layers. Referring to the example of FIG. 8, acontact fill metal 802 is provided filling the contact opening 212. Thedeposited fill metal may be planarized to form the contact structure 902including the fill metal 802 and liner layer 702.

In some implementations of the method 100, additional layers of amultilayer interconnect (MLI) feature are formed on the substrate. TheMLI feature electrically couples various components of the device 200,such that the various components are operable to function as specifiedby design requirements of the device 200. The MLI feature can include acombination of metal layers and ILD layers configured to form verticalinterconnect features, such as contact structure and/or vias, and/orhorizontal interconnect features, such as lines. The various conductivefeatures include materials similar to the contact structures. In someimplementations, a damascene process and/or dual damascene process isused to form a copper-based multilayer interconnection structure. By wayof example in FIG. 9, a first metal line 904 (e.g., copper interconnectof an MLI) is formed over the contact structure 902. Interconnect line904 may be electrically coupled to the contact structure 902. AnotherILD layer 906 may be disposed over the dielectric layer 212.

Thus, an embodiment of the method 100 provides for configuring a linerlayer profile such that it may be in some embodiments suitable foradhesion and/or diffusion barrier, but reduced in thickness at an upperportion of the opening.

In another embodiment of the method 100, the method 100 progressessimilarly to as discussed above except that an additional selective etchstep is performed after the masking layer is removed in block 112 of themethod 100. That is, the method 100, in some embodiments, proceeds toblock 114 of FIG. 1 after the masking layer is removed in block 112 (andprior to the deposition of material the liner layer in block 116discussed above). Block 114 includes removing additional portions ofmaterial of the liner layer from the sidewalls of the opening. In anembodiment, the liner layer is completely removed from the sidewalls ofthe opening above a thickness of the liner layer disposed at the bottomof the opening. The portion of the liner layer remains at the bottom ofthe opening in order to protect underlying source/drain features (e.g.,silicide/epitaxial layers of the source/drain) and/or gate layers suchas metal layers (e.g., work function) of the gate structure. Thus, in anembodiment of the method 100, there is a two-step etch back process ofthe liner layer (e.g., block 110 and block 114).

At block 114, the removal of the additional portions of the liner layeris performed by an etching process. The etching process may use adifferent chemical than that of block 110. In an embodiment, the etchingrate of the etching process of block 114 is slower than the block 110with respect to the material of the liner layer. In an embodiment, theetching process of block 114 is wet etch for example, applying peroxideto the substrate.

Referring to the example of FIG. 10, a device 200′ is provided that issubstantially similar to the device 200 discussed above. In fact, insome embodiments, the device 200′ is fabricated from the device 200 ofFIG. 6 discussed above. More specifically, providing the device 200 ofFIG. 6 to block 114 allows for an additional etch of the remaining linerlayer 502. FIG. 10 of the device 200′ illustrates the etched liner layer502, which as illustrated in FIG. 6, is removed from on a bottom portionof the sidewalls of the opening 214. The liner layer, denoted 1002 inFIG. 10, remains at a bottom (e.g., bottom surface) of the opening 214.

In some embodiments, with the deposition of the first liner layer (block106), a directional plasma treatment may be performed to alter the etchselectivity of portions of the first liner layer. In an embodiment, thedirectional plasma treatment enhances the etch selectivity between theliner layer formed on the sidewalls of the opening and the liner layerformed on the bottom of the opening. In some embodiments, the linerlayer on the sidewalls composition is modified such that it may be moreeasily etched. This can be beneficial in removing the portion of theliner layer abutting the bottom portion of the opening sidewalls whilemaintaining a portion of the liner layer at the bottom of the opening,as illustrated above.

After the removal process of block 114, the embodiment of the method 100proceeds to block 116 where material of the liner layer is depositedagain. Block 116 may be substantially similar to as discussed above.Using the example of FIG. 11, a liner layer 1100 is formed by depositingliner layer material in the opening 214 including on the sidewalls andthe bottom of the opening and over the liner layer 1002 (FIG. 10)remaining at the bottom of the opening. In an embodiment, a thickness ofapproximately t7 of liner material is deposited. Thus, provided is aliner layer 1100 having a thickness t7 on the sidewalls of the opening214 and a thickness t8 at the bottom of the opening. t8 is greater thant7. In an embodiment, the ratio of t7 to t8 is 1 to 2.

The embodiment of method 100 then proceeds to block 118 where a metalfill process is performed. Block 118 may be substantially similar to asdiscussed above. FIG. 12 is illustrative of the device 200′ afterfilling the opening 214 with fill metal 802, discussed above. Thecontact structure 1202 includes the fill metal 802 and the configuredliner layer 1100.

Thus, another embodiment of the method 100 also provides for configuringa liner layer profile such that it may be in some embodiments suitablefor adhesion and/or diffusion barrier, but reduced in thickness at anupper portion of the opening as well as a lower sidewall portion of theopening.

Illustrated in FIGS. 13, 14A, 14B, 14C, 15A, 15B, and 15C are respectivesemiconductor devices according to one or more aspects of the presentdisclosure. FIG. 13 illustrates a portion of an exemplary FINFET device1300 that maybe fabricated using one or more aspects of the presentdisclosure. FIGS. 14A and 15A are cross-sectional views of differentembodiments of the device along the direction of A-A′ cut (thoughillustrating two gate structures), which is along the fin or channel ofthe device. FIGS. 14B and 15B are cross-sectional views of differentembodiments of the device along the B-B′ cut, which is along the gatecontact. FIGS. 14C and 15C are cross-sectional views of differentembodiments of the device along the C-C′ cut, which is along thesource/drain contact structure (y-axis). It is noted that while FIGS.14C and 15C provide for a contact structure interfacing a plurality ofsource/drain features 206, this is illustrative only and not intended tobe limiting; the contact feature may interface a single source/drainfeature 206 in other embodiments.

The devices of FIGS. 13-15C may be fabricated using one or more of thesteps of the embodiments of the method 100 discussed above. Inparticular, FIGS. 14A, 14B, and 14C provide an exemplary embodiment ofthe device 200; FIGS. 15A, 15B, and 15C provide an exemplary embodimentof the device 200′. Features may be annotated using the same referencesnumbers above for ease of understanding and avoiding repetition.

As stated above, illustrated in FIGS. 13-15C is a FinFET device 1300.The FinFET device 1300 may be an embodiment of the device 200 and/ordevice 200′ discussed above. The FinFET device 1300 includes one or morefin-based, multi-gate field-effect transistors (FETs). The FinFET device1300 includes the substrate 202 having at plurality of fins extendingtherefrom, isolation regions 1302 interpose the fins, the gate structure204 including spacer elements 210 is disposed on and around thefin-element(s). Each of the plurality of fins of the substrate 202 alsoinclude source/drain regions 206 where the source/drain features areformed in, on, and/or surrounding the fin. The source/drain regions 206may be epitaxially grown on the fins 202. The source/drain regions 206may include a silicide region 208 where a contact is to be formed.

The FinFET device 1300 in an embodiment, such as shown in FIGS. 14A,14B, and 14C, includes contact structures 902. The contact structures902 may be configured substantially similar to as discussed above withreference to FIGS. 2-9. The FinFET device 1300 in an embodiment, such asshown in FIGS. 15A, 15B, and 15C, includes contact structures 1202. Thecontact structures 1202 may be substantially similar to as discussedabove with reference to FIGS. 2-6 and 10-12.

While the forgoing illustrates examples of using the liner layer to forma contact structure, the method 100 and/or aspects of the devicesillustrated may also be used with respect to other openings, holes ortrenches that are filled in the semiconductor device fabricationprocesses. As but one example, the method 100 may be used to form layersof a metal gate within a trench provided by a replacement gate process.Thus, a liner layer may be deposited and etched (e.g., in a 1-step or2-step process) before filling the remaining trench with metal gatelayers (e.g., work function). The foregoing outlines features of severalembodiments so that those skilled in the art may better understand theaspects of the present disclosure. Those skilled in the art shouldappreciate that they may readily use the present disclosure as a basisfor designing or modifying other processes and structures for carryingout the same purposes and/or achieving the same advantages of theembodiments introduced herein.

In one embodiment of the present disclosure, provided is a method thatincludes forming an opening in a layer over a semiconductor substrate.The opening has a sidewall and a bottom. A first deposition processforms a layer of material of a first composition on the sidewall and thebottom. A masking layer is formed in the opening over the layer. A firstportion of the layer is etched while using the masking layer to protecta second portion of the layer. The masking layer is removed to exposethe second portion of the layer. A second deposition process isperformed to deposit material of the first composition over the secondportion of layer and on the sidewall of the opening. After performingthe second deposition, the opening is filled with a conductive material.

In another embodiment, a method is provided that includes providing asubstrate having a gate structure and a source/drain region. Adielectric layer is deposited over the substrate, the gate structure,and the source/drain region. A first opening is etched in the dielectriclayer exposing a top surface of the gate structure and a second openingis etched in the dielectric layer exposing a top surface of thesource/drain region. A first portion of a liner layer is deposited inthe first opening and the second opening. Thereafter, a top region ofthe first portion of the liner layer is removed from the first openingand the second opening. The top region interfaces a top portion ofsidewall of the first and second openings. A second portion of the linerlayer is deposited after removing the top region. The first and secondportions of the liner layer provide a first thickness on the top portionof the sidewall of the first and second openings and a second thicknesson a bottom of the first and second openings, the second thickness beinggreater than the first thickness.

Also provided is an embodiment of a semiconductor device that includes agate structure and a source/drain region adjacent the gate structure. Afirst contact structure interfaces the gate structure. The first contactstructure includes a liner layer having a first thickness at an upperportion of the first contact structure and a second thickness at abottom of the first contact structure. The second thickness is greaterthan the first thickness. A conductive fill layer is disposed over theliner layer.

Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A semiconductor device, comprising: a gatestructure and a source/drain region adjacent the gate structure; and afirst contact structure over the gate structure and extending tointerface a top surface of the gate structure, wherein the first contactstructure includes: a liner layer having a first thickness at an upperportion of the first contact structure and a second thickness at abottom portion of the first contact structure, wherein the secondthickness is greater than the first thickness; and a conductive filllayer over the liner layer.
 2. The semiconductor device of claim 1,further comprising: a second contact structure interfacing thesource/drain region, wherein the second contact structure includes: theliner layer having the first thickness at an upper portion of the secondcontact structure and the second thickness at a bottom portion of thesecond contact structure; and the conductive fill layer over the linerlayer.
 3. The semiconductor device of claim 1, wherein the liner layerof the first contact structure has the second thickness of a firstcomposition and the first thickness of the first composition.
 4. Thesemiconductor device of claim 2, wherein the bottom portion of thesecond contact structure having the liner layer of the second thicknesshas a height greater than the gate structure.
 5. The semiconductordevice of claim 1, wherein the liner layer includes TiN.
 6. Thesemiconductor device of claim 1, wherein the liner layer of the firstcontact structure has the second thickness on a bottom portion of asidewall of the first contact structure and the second thicknessextending across a bottom surface of the bottom portion of the firstcontact structure to a bottom portion of an opposing sidewall of thefirst contact structure.
 7. The semiconductor device of claim 1, whereinthe liner layer includes titanium.
 8. The semiconductor device of claim1, wherein the liner layer is a multi-layer structure including atitanium layer and a titanium nitride layer.
 9. A semiconductor device,comprising: a gate structure and a source/drain region adjacent the gatestructure; and a first contact structure interfacing the source/drainregion, wherein the first contact structure includes: a liner layeralong sidewalls of the first contact structure, wherein the liner layerhas a first thickness at an upper portion of the sidewalls and a secondthickness at a lower portion of the sidewalls, wherein the secondthickness is greater than the first thickness, wherein the lower portionof the sidewalls of the first contact structure having the liner layerwith the second thickness has a height greater than the gate structure;and a conductive fill layer over the liner layer.
 10. The semiconductordevice of claim 9, wherein the liner layer has the second thickness at abottom surface of the first contact structure.
 11. The semiconductordevice of claim 10, wherein the liner layer at the bottom surfaceinterfaces a silicide region.
 12. The semiconductor device of claim 9,wherein the source/drain region includes a silicide region.
 13. Thesemiconductor device of claim 12, wherein the liner layer interfaces thesilicide region.
 14. The semiconductor device of claim 13, wherein thesource/drain region further includes an epitaxially grown material underthe silicide region.
 15. A semiconductor device, comprising: a firstcontact structure interfacing a semiconductor device feature, whereinthe first contact structure includes: a liner layer having a firstcomposition with a first thickness at an upper portion of the firstcontact structure and the first composition with a second thickness at abottom portion of the first contact structure, wherein the secondthickness of the first composition is greater than the first thicknessof the first composition, wherein the first composition includes atleast one of titanium or tantalum; and a conductive fill layer over theliner layer.
 16. The semiconductor device of claim 15, wherein thesemiconductor device feature includes one of a gate structure of asource/drain feature.
 17. The semiconductor device of claim 15, whereinthe first composition is titanium nitride.
 18. The semiconductor deviceof claim 17, wherein the titanium nitride interfaces a silicide regionof the semiconductor device feature.
 19. The semiconductor device ofclaim 15, wherein the first composition includes tantalum nitride TaN.20. The semiconductor device of claim 15, wherein the conductive filllayer includes aluminum, aluminum alloy, copper, copper alloy, titanium,titanium nitride, tantalum, tantalum nitride, tungsten, polysilicon, ormetal silicide.